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Stormy Week

May 19, 2017

Stormy Week:

Monday through Wednesday of this week (May 15-17) brought severe weather to the region, including strong thunderstorms, large hail, flash flooding, and tornadoes. The tornadoes occurred in western Wisconsin (Polk, Barron, and Rusk Counties) on May 16th, with the most damage coming from an EF-2 storm (winds 111-135 mph) that passed through Chetek, WI destroying a mobile home park, injuring over 20 people, and causing one death. On the same date large hail was reported from many eastern Minnesota communities, including 2.5 inch diameter hail near Northfield. On May 17th two short-live tornadoes were reported in southeastern Minnesota, one near Plainview and one near Elgin. Both caused some minor damage. A summary can be found at the NOAA-NWS-La Crosse, WI web site.

Many other observers reported total amounts of rainfall this week that exceeded 3 inches. The heavy rains brought a halt to planting of crops around the state, although corn planting is close to being finished, and soybean planting is more than half done. Over 40 climate stations in Minnesota have already seen about normal May rainfall amounts, and that is just for the first 18 days of the month.

Weather Potpourri:

Speaking of tornadoes, a recent study by researchers at Florida State University documents the relationship between total storm energy (calculated using total path area and average wind speed) and human casualties. This study incorporated the analysis of 872 tornadoes between 2007 and 2015.

NOAA referenced a new tool this week that schools can use to be more sustainable and environmentally friendly. It is called "12 Steps to a Sustainable School" and worth a look.

The World Meteorological Organization announced this week an assessment of world weather records that produced the highest mortality associated with tropical storms, lightning, tornadoes, and hailstorms.

A recent study in Environmental Research Journal documents that Heat Index values between 90 and 100 degrees F or greater have serious detrimental health effects on many residents of New England. This study has provoked the National Weather Service to reconsider forecast thresholds for issuing Heat Advisories in many New England states. The authors encourage more regional studies to tailor advisories to the various tolerances that communities have for stress.

MPR listener question:

My 5th grader wants to know how much a cloud weighs. Can you help?

Answer:

Yes, a number of years ago NOAA's Thomas Schlatter wrote about this in Weatherwise magazine. So I will use his example.

He estimated the liquid water content of a cumulus cloud to be about 0.2 grams/cubic meter and then estimated the cloud volume to be about 1 cubic km (approximately one quarter of a cubic mile), which is a relatively small cumulus cloud. A computation of the mass of water contained in this cloud yields 200,000 kilograms or 441,000 pounds of water, enough to fill a large residential swimming pool. Most of these water droplets in the cloud are so small, that minor updrafts are sufficient to keep them suspended in the air for long periods of time.

Twin Cities Almanac for May 19th:

The average MSP high temperature for this date is 70 degrees F (plus or minus 11 degrees F standard deviation), while the average low is 50 degrees F (plus or minus 8 degrees F standard deviation).

Average dew point for May 19th 21st is 45°F; the maximum dew point on this date is 66°F in 2004; and the minimum dew point on this date is 11°F in 1926.

All-time state records for May 19th:

The all-time state high temperature for today's date is 104 degrees F at Redwood Falls (Redwood County) in 1934; the all-time state low for today's date is 16 degrees F at Embarrass (St Louis County) in 2002. The all-time state record precipitation for this date is 4.17 inches at St Francis (Anoka County) in 1996. The all-time state record snowfall for this date is 8.6 inches at Grand Rapids (Itasca County) in 1971.

Past Weather Features:

On May 19, 1924 a hard freeze came to portions of northern and western Minnesota damaging newly emerged crops. Temperatures fell below freezing as far south as Fairmount, and in the north along the Canadian border temperatures fell into the teens F.

The warmest May 19th in state history was in 1934 when over 30 climate stations reported daytime high temperatures of 90 degrees F or higher. Ten western Minnesota communities reached 100 degrees F or higher.

An almost winter-like storm brought snow to the state over May 19-20, 1971. Many climate observers reported 1 to 4 inches, while some parts of the Iron Range in northeastern Minnesota reported 6 to 8 inches of snow. Temperatures rose into the 60s F the next day, rapidly melting all of the snow.

May 19, 2009 brought highly variable weather conditions to Minnesota. At 4pm in the afternoon it was 100 degrees F at Milan and Madison in the western part of the state and just 45 degrees F at Isabella in the northeast.

Outlook:

Cloudy with showers on Saturday. Cooler than normal temperatures. Still a chance for showers on Sunday, but slightly warmer temperatures. Warmer yet on Monday with near normal temperatures. Chance for showers and thunderstorms later in the day. Drier weather next Tuesday through Thursday, with cooler than normal temperatures.